The present invention relates to an information recording/reproducing optical disk for recording/reproducing information on/from a sector arranged along a spiral track as an information unit, and an information recording/reproducing device using this disk.
A commercially available, rewritable optical disk for recording/reproducing information includes a magneto-optical disk having 120 or 90 mm in diameter and a phase transition disk (PD) having 120 mm in diameter.
On these disks, a guide groove for guiding a laser beam radiation is formed. Diffraction of the laser beam by the guide groove is used to carry out tracking. This guide groove is formed in a continuous spiral form from the inner peripheral portion of the disk toward the outer peripheral portion thereof. The guide groove is simply called a "groove" and the portion which is not the guide groove is called a "land". In the prior optical disk, information is recorded on either one of the groove or land.
Information on such an optical disk is read and recorded, for example, by unit of 512 bytes or 2048 bytes. The information unit of a group of such bytes is called a "sector". Sector addresses which indicate respective addresses of the sectors are assigned to the sectors, respectively. In order to record information on a target address and reproduce the information with high reliability, the sectors are formatted in accordance with a specified sector format. In formatting, information on the sector address is recorded by forming a recess called a pit at the head of each of the sectors. The section at which the sector address information is recorded is called a "header". As described above, in the prior optical disk, information is recorded on either one of the groove or the land (i.e., groove recording or land recording). As a result, the header is also arranged at only the groove in the case of the groove recording, and at only the land in the case of the land recording.
If information is recorded on both of the land and the groove, which is different from the prior optical disk, it can be easily expected that more recording capacity can be realized.
However, a subject for making it possible to record information on both the land and groove is a method for forming sector addresses. Details thereof will be described below.
In the above-described prior optical disk on which the spiral groove is formed, the groove and the land are formed in parallel. The groove and the land are spiral tracks which can be traced in parallel. In other words, a spiral track of each of the groove and the land is formed on the disk. Thus, the structure of the prior optical disk is referred to as a "double spiral structure".
Since the groove and the land are formed in parallel in the double spiral structure, track jump is indispensable in shift from the groove to the land. Therefore, when recording/reproducing information on/from the groove is switched to recording/reproducing information on/from the land or vice versa, track jump or seeking is necessary so that successive record or reproduction of the information is difficult.
In order to format a disk having this double spiral structure, there is only a method of formatting sectors on the groove (called "groove sectors" hereinafter) and sectors on the land (called "land sectors" hereinafter) separately. This results in an inconvenience, for example when the disk is formatted so as to record/reproduce information alternately, in a zone CAV manner, on/from the groove and land which are adjacent to each other.
Specifically, in order that the adjacent land and groove have successive sector addresses, it is necessary to format only the groove and format only the land, while assigning intermittent addresses every track cycle. In this case, difficult is the formatting for performing position-matching accurately at the connecting points where addresses are successive from the land to the groove or vice versa. If, in recording/reproducing information, the shift from the land to the groove or from the groove to the land is not smoothly performed, the wait for rotation of the disk is unavoidable so that continuous record/reproduction of the information is obstructed.
In order to overcome these problems, an object of the present invention is to provide an information recording/reproducing optical disk having large recording capacity and a high speed access and making it possible to record and reproduce successive information with high reliability.
Another object of the present invention is to provide an information recording/reproducing device for precisely recording/reproducing information on/from such an optical disk at a high speed.